This invention relates to a zippered bag, and more particularly, gusset bag provided with a zipper element for opening or closing an end opening of the bag through which a content filling in the bag can be easily taken out, and also is concerned with a method of forming such zippered bag.
In the known art, there has been provided a flat bag container having opposing flat portions, and four side peripheries of such bag are heat sealed (four side seal bag), and an opening of the bag through which an inner content can be taken out is closed or opened by providing a zipper element. With such flat bag, it is possible to manufacture the bag by making coincident the delivery direction of a film material forming a flat bag container with a supply direction of the zipper element, thus being advantageous in a productivity.
Further, recently, it is attempted to apply the zipper element to a bag other than the four side seal bag, and in such attempt, a cap shaped bag member provided with a zipper element is preliminarily prepared and the cap shaped bag member is then applied to a bag body prepared separately from the cap shaped bag member. For example, a gusset bag provided with gores at both side portions of the bag body has a good self-supporting property and a relatively large inner capacity, and accordingly, the usage thereof is widened and the application of the zipper element to the gusset bag has been desired.
However, since the gusset bag has a folded portion as gusset, it involves a problem of difficult attachment of the zipper element and many other points to be improved for the structure of such gusset bags.